In a large ovenproof non-stick or cast-iron skillet, heat 2,5 tablespoons oil over medium-high heat. Add the onion and garlic and season with salt; cook, stirring occasionally, until softened, about 4 minutes.

Add the potatoes, red pepper, an additional 2 tablespoons oil, and season with pepper and 1/2 teaspoon salt, or to taste. Cook, stirring occasionally, for 25 minutes, or until the potatoes are tender and lightly browned in places.

Meanwhile, preheat the oven to 450°F / 230°C.

Transfer the potato mixture to a large bowl and let cool slightly.

In a second bowl, lightly beat together the eggs with the smoked paprika and a pinch of salt and pepper, then add to the bowl with the potato mixture.

Return the skillet to medium-high heat and once hot add the potato and egg mixture to the pan. Sprinkle the grated cheese over top (alternatively, add to the egg mixture), if using.

Lower the heat to medium and cook until the eggs start to set (about 2 minutes). Let the eggs slowly cook, shaking the skillet occasionally, until the eggs are halfway cooked, about 5 minutes. You will see the egg set around the edges of the skillet and when you shake the skillet, the egg mixture will not be as loose or jiggly.

Transfer the skillet to the preheated oven and cook until the top of tortilla is just set, 3-4 minutes. Turn the heat to broil and cook until the top is beginning to lightly brown in places and the tortilla seems fully set when the pan is shaken, 2-4 minutes.

Let cool, garnish with a little parsley, then using a spatula, divide the tortilla into pieces. Serve and enjoy!